Synthesis of Pyrrole Derivatives through Functionalization of 3,4‐Bis(lithiomethyl)dihydropyrroles

Bis(2‐lithioallyl)amines 2 , substituted at the double bonds, undergo intramolecular carbolithiation of a lithiated double bond in different solvents to afford dilithiated dihydropyrroles 3 . Treatment of these dianions with electrophiles allows the preparation of functionalized pyrrole derivatives 5 and 6 . Interestingly, treatment of these dianions with carboxylic esters selectively affords either keto or hydroxy compounds ( 9 or 10 ), depending on the conditions. Several experiments have been carried out in order to clarify the mechanism of this selective transformation. Finally, dilithiated dihydropyrrole 3a could be transformed in a three‐step procedure into the corresponding 3,4‐bis(bromomethyl) derivative 31 , which can easily be converted into bicyclic pyrrole compounds 32−33 by treatment with different nucleophiles. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)